How are the placements at IIT Patna CSE? At the official website, it is 24.2 LPA. Is it legit?

These figures are very much misleading. These packages are CTC (Cost to Company) and the in-hand package may differ a lot. If you want more information about CTC, you can look for it. Just take care that even someone with a CTC of 50 LPA, may only get in-hand 1 lakh monthly.